Decolorization of extracts containing tannin.



ARMAND JULIUS STIEGELMAXN AND ERICH. DEHNEL, O1?LUDWIGSHAFEN-ON-THE-RHINE,

GERMANY, ASSIGNORS TO BADISCHE-AXILIN d: SODA FABRIK, OF LUDWIGSHAFEN-ONTHE-RHIXE, GERMANY, A CORPORATION.

DEGGLORIZATIQN U36 EXTRACTS ()GNTAINING TANNIN.

Specification of Letters Patent.

Patented May 26, 1908.

Appllization'filed July 12, 1906. Serial No.325,939.

1c The extracts obtained from barks which containtannin are 111 manycases so strongly colored. that they are unsuitable tor use for.

tanning leather, because they discolor the leather. Attempts have beenmade to decolorize the said extracts by means of sulfurous acid, or of ahydrosulfite, but these either produce no decolorization, or any resultsobtained are not permanent becausethe coloring matter is merely reducedWithout being destroyed.

We have discovered that extracts containing tannin can be decolorizedandexcellent and permanent results obtained; by treatin such extracts witha formaldehyde sulfoxy ate, oixwith a formaldehyde hydrosulfite compound(that is, formaldehyde sulfoxylate, and formaldehyde bisulfite,chemically, or otherwise united), which can be done for example byallowing; the formaldehyde compound selected. to'react, While theextract is being evaporated by means of heat. Sodium formaldehydesulfoxylate (rongalite C) and sodium formaldehyde hydrosulfite(hydrosulfite N. F., or hyraldite A) are, on account of their solubilityin Water,

very suitable for use in carrying out our invention, but thecorresponding salts of other metals such for instance as those of zinc,calcium, and barium, can also be used.

40 hese latter act more slowly, but possess the advantage that the metaleither separates out, of its own accord, in the form of airinsolublecompound, or can be subsequently precipitated and removed by filtration.As is Well known, formaldehyde liydrosulfite behaves as if it were acombination of molecular proportions of formaldehyde sulfoXy late andformaldehyde bisullite, consequently for the purposes of this inventionformaldehyde sulfoxylate and formaldehyde hydrosulfite are equivalent.

The following are examples of how our invention. can be carried intopractical effect. but our invention is not confined to these examples.

Example 1: To one (1) liter of an aqueous extract of chestnut Wood (offour (a) degrees Baum) add five (5) grams of rongalite C (containingninety (90) per cent. of sodium formaldehyde sulfoXyla-te) and evapcrate the hole to dryness in vacuo.

Example 2: To one (1) kilogram of an aqueous extract of quebracho (offour (4) degrees Baum) add twenty (20) grams of basic zincformaldehydesulfoxylate, heat for some time, filter oil the solidresidue, and evaporate the filtrate till the desired concentration hasbeen attained.

Now What we claim is:

The process of decolorizing extracts containing tannin consisting inheating the said extracts in a ueous solution with a formaide- I hydesulfoxy ate.

In testimony whereof We have hereunto set our hands in the presence oftwo subscribing Witnesses.

ARMAIH} JULIUS STlEGEhlllAllll. cries DEHNEL.

Witnesses ERNEST l EHRHARDT, J. Auto. LLQYD.

